1. Field of the Invention
This invention relates to virtual ports connecting peripheral devices to computers. More particularly, it relates to a device driver arrangement that retains a virtual serial port when a peripheral device is disconnected from the computer.
2. Background Information
In the past, and to some extent the present, peripheral devices have been connected to computers by way of hardware serial ports designated with “com port” numbers. The software applications that make use of these peripheral devices communicate with them by way of software devices drivers. These peripheral devices are termed “built in” because the system will not respond to the plugging or unplugging of the devices while system is operating.
More recently, “hot-pluggable” devices have been introduced by way of USB (Universal Serial Bus) hardware ports and “Plug-N-Play” software included with operating systems such as the Windows 2000™ and Windows XP™ systems marketed by Microsoft Corporation. When a hot-pluggable device is connected to the computer, the operating system kernel installs a device driver particular to that device. In this case the driver also functions as a virtual corn port that interacts with the user application as though it were a hardware corn port in a built in arrangement.
If the device is detached from the computer during computer operation, the computer causes the associated driver to remove itself and this removes the virtual corn port function provided by the driver. This may cause malfunction because some applications, require a corn port connection even if a corresponding device has been detached.